Darling moves from The Adoption Papers, Jackie Kay's highly autobiographical collection with which she burst on to the British poetry scene at the start of the 1990s, to recent, uncollected poems. In between are selections from her three subsequent collections for adults, reproduced pretty much entire; and four written for young people. The result - thanks in part to Bloodaxe's distinctive pile-'em-high layout - is satisfyingly compendious.

It's a rare, and indeed a brave, poet who includes work for children in a Selected. And it's a rarer figure still whose verse for young people and adults makes such common cause that this selection not only achieves coherence, but serves to illustrate her true strengths. Kay's Darling locates her alongside Ted Hughes - even TS Eliot - in that elite group whose children's writing, rather than gainsaying their primary poetic project, informs and enriches it. If the Hughes of What Is the Truth? reads like the poet of Moortown slowed to a lucent focus, the opening of "My Face Is a Map", from Red, Cherry Red (2007), will be instantly recognisable to Kay's adult readers: "I was born with a map of Australia on my face; / it was beautiful, my mother told me, / there was nobody like me in the whole wide world / who could trace the edges of down under / on the raised and grafted song lines of her face."

Some of what makes this poem, ostensibly about facial deformity, so recognisable is thematic. Place, the degree to which we incarnate it - whether through ethnicity or in our behaviour and language - and, in particular, redemptive recognition by a female principle ("it was beautiful, my mother told me") are Kay's preoccupations. Darling illustrates how they continue to inform her work right up to the new, unpublished love poems. In "Stars, Sea", "Winter Heart" and "First Light", the lover's body is not merely situated "not so far from Cardigan Bay", "in the room", "In the morning", but itself becomes a place to arrive at "As if every lover we had ever loved / Was here, or coming in".

Though the iteration of questions about belonging seems at times richly self-referential - as in the punning title of 1998's Off Colour, a collection that divides its attention between what we already know of the authorial body and its potential malaises - this never contracts into solipsism. Indeed, the opposite is true: one of Kay's greatest strengths is the way she locates individual experience in the collective. As befits an adoptive daughter of peace marchers, Kay is a writer for whom the personal is indeed political. The famous "Adoption Papers" sequence, with its three narrators - birth mother, adoptive mother, daughter - is a clear homage to Sylvia Plath's "Three Women: A Poem for Three Voices", set on a maternity ward. But, while Plath's is a complex, inflected exploration of individual sensibilities, Kay also takes in that surrounding chorus - of teachers, school friends and neighbours - which we call "society".

Even such a public poet as Kay, though, writes verse shaped above all by human cadence. She has an immaculate ear for speech patterns, using accent and dialect, in particular, to lift and characterise. When "Maw Broon Visits a Therapist", the brow-beaten housewife confesses, "When it comes tae talking aboot me, / well, A' jist clam up. Canny think whit / tae say." This is more than mere ventriloquism. Language shifts to record a culture but also a psyche. Throughout the Maw Broon poems enjambment gives us the back-and-forth of their narrator's uncertain humility. And to read Kay's work, as it is collected here, is to recognise how much of it is written in persona. It would be hard to think of a contemporary poet whose narrator so thoroughly appropriates what might otherwise remain extra-textual. Far from confessional surrender, this strategy allows the writer to construct and control her own authorial presence. Material normally open to speculative literary biography - Kay's adoption, her ethnicity, sexuality, even her own parenting - is rehearsed, and therefore to some degree determined, on the page.

This isn't to suggest Kay is somehow an "inauthentic" writer: far from it. Her commitment to forms of linguistic music - especially those derived from childhood - plays a major role in making her the highly influential poet she is. It extends, after all, a deep-seated tradition within 20th-century British verse. WH Auden and George Mackay Brown are as audible as AE Housman or Rudyard Kipling behind the blues of Kay's Bessie Smith poems from Other Lovers (1993), in the clapping/skipping singsong that haunts 2005's Life Mask, and in the ballad and folksong that mark that collection's love poems every bit as much as they do such verses for children as "Brendon Gallacher", "The Hole Story" and "The Angler's Song".

The human cadence Kay captures, though, is not purely linguistic. Darling also describes that other arcing fall: from birth, through increasing realisations of complexity (Kay's Nigerian roots turn out not to afford any straightforward "closure") to poems of loss and grief. Relationships end, a son leaves home - and people die. The book's title poem, a touching farewell to the poet Julia Darling, embraces what is true for us all, at every time: "The dead don't go till you do, loved ones. /The dead are still here holding our hands."